JPS617070A - High-frequency high voltage generator for arc welding - Google Patents

Abstract

PURPOSE:To charge a condenser to a required voltage with a high-frequency transformer having small current capacity by operating a boosting transformer as a high-frequency transformer by a switch circuit, converting a high-frequency high voltage to DC and impressing said voltage to the condenser. CONSTITUTION:A DC high voltage generating circuit B is constituted of a high- frequency transformer 12, a switching circuit 11 which intermits periodically the primary current to the transformer 12 and a diode 13 for high voltage which is a current rectifying element to convert the high-frequency voltage induced in the secondary side of the transformer 12 to DC. The required voltage can be therefore charged to the condenser even if the current capacity of the transformer 12 is small when the high-frequency high voltage is rectified by the diode 13 and impressed to the condenser. The high-frequency oscillation current flows to the series circuit of the condenser, a discharge gap 10 and the primary side of a coupling coil 10 when the voltage of the condenser attains the discharge start voltage of the discharge gap 10. The high-frequency high voltage is then generated in the welding circuit to assist the arc start.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a high frequency and high voltage generator suitable for arc starting and arc stabilization in TIG arc welding and the like.

[Background of the Invention] FIG. 1 shows the general configuration of a conventional high-frequency, high-voltage generator for arc welding.

This figure shows nine examples used for arc starting in DC TIG welding, where 1 is a DC welding power source, 2 is a welding torch with a tungsten electrode and a gas shielding nozzle, 3 is a base material, 4 is a coupling coil, and 5 6 is a high frequency bypass capacitor, and 6 is a welding current detection circuit.

At the beginning of welding, contact 7 of welding current detection circuit 6 is closed, voltage is applied from commercial AC power supply A to the primary side of high voltage transformer 8, high voltage is generated on the secondary side, and every half wave of AC Charge capacitor 9. When the voltage of the capacitor 9 reaches the discharge starting voltage of the discharge gap 10, a high-frequency oscillating current flows through the series circuit of the capacitor 9, the discharge gap 10, and the primary side of the coupling coil 4, and the coupling coil 4 connected to the welding circuit A high frequency and high voltage is induced on the secondary side of the welding torch 2 and breaks the insulation between the electrode of the welding torch 2 and the base material 3,
Helps start the arc. When the welding current flows, the contact 7 of the welding current detection circuit 6 opens to stop the generation of high frequency and high voltage.

In such a conventional high-frequency high-voltage generator for arc welding, the high-voltage transformer 8 boosts the commercial frequency voltage, resulting in a large volume and weight (secondary output of 3 kV, several tens of mA).
(approximately 2#), which was a problem in reducing the size of the device.

[Object of the Invention] An object of the present invention is to solve the above-mentioned problems of the prior art and to realize a significant reduction in size and weight of a high-frequency, high-voltage generator for arc welding.

[Summary of the Invention] The present invention provides a high-frequency transformer, a switching circuit that periodically switches on and off the primary current of the high-frequency transformer, and a rectifier that converts the high-frequency high voltage induced in the secondary side of the high-frequency transformer into direct current. A high-frequency oscillating current is made to flow through the capacitor, the discharge gap, and the series circuit on the primary side of the coupling coil using the output of this high-voltage DC voltage generating circuit, thereby reducing the size and weight of the transformer. It is something.

[Embodiments of the Invention] Hereinafter, embodiments of the present invention will be explained in detail with reference to FIGS. 2 to 4.

Figure 2 shows an example used for arc starting in DC TIG welding, and parts corresponding to Figure 1 are designated by the same reference numerals and will not be described further.

B is a DC high voltage generation circuit provided in place of the high voltage transformer 8 in FIG.
2 and a high-voltage diode 13 which is a rectifying element. The switching circuit 11 periodically switches on and off the primary current of the high-frequency transformer 12 to generate a high-frequency voltage.
Specifically, it can be configured as shown in FIG. 3, for example.

The switching circuit 11 shown in FIG.
The commercial AC voltage supplied through the contact 7 of the welding current detection circuit 6 shown in the figure is passed through the diode 14 with a half-wavelength, and the resistor 1
5 and the primary coil of the high frequency transformer 12 to charge the capacitor 21. When the voltage of the capacitor 21 reaches a certain value, a gate current flows through the thyristor 19 through the voltage dividing resistors 16 and 17 and the constant voltage diode 18, turning the thyristor 19 on. As a result, the charge in the capacitor 21 is rapidly discharged through the thyristor 19 and the primary coil of the high-frequency transformer 12, and a high-frequency component (for example,
An oscillating current containing several hundred centimeters is applied. Reference numeral 20 denotes a diode for applying a reverse bias to the thyristor 19 and turning it off by applying an oscillating current. As a result, the high frequency high voltage induced on the secondary side of the high frequency transformer 12 is half-wave rectified by the diode 13 in this example, and generates a DC high voltage.

If the high frequency high voltage induced on the secondary side of the high frequency transformer 12 is directly applied to the capacitor 9 shown in FIG. 2 without going through the diode 13, the high frequency transformer 12
As the secondary side of the transformer approaches a short-circuit state, the current capacity of the high-frequency transformer 12 must be made extremely large in order to charge the capacitor 9 at the discharge starting voltage 1 of the discharge gap 10. It doesn't suit me.

However, if the high frequency high voltage induced on the secondary side of the high frequency transformer 12 is rectified by the diode 13 and applied to the capacitor 9 as in this example, the capacitor 9 is charged with direct current, so the current of the high frequency transformer 12 is Even if the capacitance is small, the capacitor 9 can be charged to a required voltage by switching some sections of the thyristor 19. Then, each time the voltage of the capacitor 9 reaches the discharge starting voltage of the discharge gap 10, a high-frequency oscillating current flows through the series circuit of the capacitor 9, the discharge gap 10, and the primary side of the coupling coil 4, as in the conventional example, and welding Generates high frequency and high voltage in the circuit to help start the arc.

Although FIG. 3 shows a switching circuit using a thyristor, the switching element may also be a transistor.

FIG. 4 shows another embodiment of the invention. In this actual example, a capacitor 21 is charged from a commercial AC power source through a diode 14 and a resistor 15, and a separately provided oscillator 22 turns on and off a transistor 23, which is a switching element, at high speed, and the primary By passing the discharge current of the periodic Nikon condenser 21 through the side coil, a primary NK high frequency voltage of the high frequency transformer 12 is generated. As a result, the secondary high-frequency high voltage induced on the secondary side of the high-frequency transformer 12 is half-wave rectified by the diode 13, and charges the capacitor 9 through the primary side of the coupling coil 4. This is a flywheel diode that protects the 24 transistors 23 from overvoltage.

According to this example, the number of discharges in the discharge gap 1o is determined by the oscillation frequency of the oscillator 22, for example, the oscillation frequency of the oscillator 22.
If the oscillation frequency is set to about #i to 10, the number of discharges in the discharge gap 10 can be increased to several hundred, so that arc starting can be performed more reliably.

The high-frequency high-voltage generator according to the present invention can be used not only for DC TIG welding but also for arc starting AC TIG welding, CO2 welding, etc., and can also be used for arc starting such as AC TIG welding and CO2 welding. If it remains closed, AC TIG
It can also be used to stabilize the arc of welding.

[Effects of the Invention] According to the present invention, the excitation magnetic flux of the transformer can be kept low by using a switching circuit that periodically intermittents the primary side current of the transformer and using a high-frequency transformer as the transformer for external use. By converting the high frequency high voltage induced in the side to direct current and applying it to the capacitor, the capacitor can be charged to the required voltage even if the current capacity of the high frequency transformer is small. For example, the volume of a comparative transformer,
It becomes possible to reduce the weight to a fraction of that, and the entire device can be made significantly smaller and lighter.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a conventional example of a high frequency high voltage generator for arc welding, FIG. 2 is a circuit diagram showing an embodiment of the present invention,
Figure 3 is a detailed diagram of the DC high voltage generation circuit in Figure 2.
The figure is a circuit diagram showing another embodiment of the present invention. B... DC high voltage generation circuit, 11... Switching circuit, 12... Akane frequency transformer, 13... High frost that is a rectifying element; voltage diode, 9... Capacitor 10... Discharge cap , 4...Coupling coil. Figure 1

Claims (1)

[Claims] A DC high voltage generation circuit consisting of a high frequency transformer, a switching circuit that periodically switches on and off the primary side current of the high frequency transformer, and a rectifier that converts the high frequency high voltage induced on the secondary side of the high frequency transformer into DC. A high-frequency high-voltage generator for arc welding, comprising: a high-frequency oscillating current flowing through a series circuit of a capacitor, a discharge gap, and a primary side of a coupling coil by the output of the DC high-voltage generating circuit.